Apparatus and method for depositing thin film on wafer using atomic layer deposition

ABSTRACT

An atomic layer deposition (ALD) thin film deposition apparatus including a reactor in which a wafer is mounted and a thin film is deposited on the wafer, a first reaction gas supply portion for supplying a first reaction gas to the reactor, a second reaction gas supply portion for supplying a second reaction gas to the reactor, a first reaction gas supply line for connecting the first reaction gas supply portion to the reactor, a second reaction gas supply line for connecting the second reaction gas supply portion to the reactor, a first inert gas supply line for supplying an inert gas from an inert gas supply source to the first reaction gas supply line, a second inert gas supply line for supplying the inert gas from the inert gas supply source to the second reaction gas supply line, and an exhaust line for exhausting the gas from the reactor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an atomic layer deposition (ALD) thinfilm deposition apparatus for depositing a thin film on a semiconductor,for example, on a semiconductor wafer, and a method thereof.

2. Description of the Related Art

A thin film deposition apparatus forms a predetermined thin film on awafer by supplying reaction gases to the wafer received within areactor. This thin film deposition apparatus includes a chemical vapordeposition (CVD) thin film deposition apparatus, an atomic layer epitaxy(ALE) thin film deposition apparatus, and others, and has been appliedto various fields for manufacturing semiconductor devices.

Thin film deposition apparatuses have been continuously improved to makea highly-integrated chip and increase the efficiency of management andproductivity.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide an ALD thin filmdeposition apparatus and a method thereof, by which a thin film havingexcellent electrical characteristics, a high purity, in which impuritiesare removed as much as possible, and an excellent step coverage can beformed, and the efficiency and productivity of management can beimproved.

Another objective of the present invention is to provide an ALD thinfilm deposition apparatus including an exhaust line for continuouslymaintaining a desired process pressure before and after depositing athin film, and pumping a reactor, and a deposition method.

To achieve the above objectives, the present invention provides anatomic layer deposition (ALD) thin film deposition apparatus including:a reactor in which a wafer is mounted and a thin film is deposited onthe wafer; a first reaction gas supply portion for supplying a firstreaction gas to the reactor; a second reaction gas supply portion forsupplying a second reaction gas to the reactor; a first reaction gassupply line for connecting the first reaction gas supply portion to thereactor; a second reaction gas supply line for connecting the secondreaction gas supply portion to the reactor; a first inert gas supplyline for supplying an inert gas from an inert gas supply source to thefirst reaction gas supply line; a second inert gas supply line forsupplying the inert gas from the inert gas supply source to the secondreaction gas supply line; and an exhaust line for exhausting the gasfrom the reactor.

To achieve the above objectives, the present invention provides an ALDthin film deposition method including: mixing a first reaction gas andan inert gas to form a first mixture gas; supplying the first mixturegas to an upper surface of a wafer received in a reactor; mixing asecond reaction gas and the inert gas to form a second mixture gas; andsupplying the second mixture gas to edges of the wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objectives and advantages of the present invention will becomemore apparent by describing in detail preferred embodiments thereof withreference to the attached drawings in which:

FIG. 1 is a schematic diagram of an atomic layer deposition (ALD) thinfilm deposition apparatus according to a first embodiment of the presentinvention;

FIG. 2 is an exploded perspective view of a reactor in the ALD thin filmdeposition apparatus of FIG. 1;

FIG. 3 is an exploded perspective view of a shower head plate and adiffusion plate in the reactor of FIG. 2;

FIG. 4 is a cross-sectional view of the reactor of FIG. 2;

FIG. 5 is a magnified cross-sectional view of the first mixing unit ofthe reactor of FIG. 4;

FIG. 6 is a graph showing the relationship between an interval (D) and aspecific resistance while a thin film is deposited;

FIG. 7 shows a reactor combined with a transfer module through a vatvalve;

FIG. 8 is a cross-sectional view of an ALD thin film depositionapparatus according to a second embodiment of the present invention; and

FIG. 9 is a cross-sectional view of an ALD thin film depositionapparatus according to a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an atomic layer deposition (ALD) thin film depositionapparatus that can deposit a TiN or TaN thin film on a wafer. Depositionof a TiN thin film will now be described as an example. In order to forma TiN thin film, TiCl₄ is used as a first reaction gas, NH₃ is used as asecond reaction gas, and Ar is used as an inert gas.

Referring to FIG. 1, an ALD thin film deposition apparatus includes areactor 100 for receiving a wafer and depositing a thin film on thewafer, a gas jungle (this term was made by the present inventor todescribe complicatedly-connected gas lines) for supplying a reaction gasto the reactor 100, and an exhaust line 400 for exhausting the gaswithin the reactor 100 to the outside.

FIG. 2 is an exploded perspective view of a reactor in the ALD thin filmdeposition apparatus of FIG. 1. FIG. 3 is an exploded perspective viewof the reactor of FIG. 2, in which a shower head plate is separated froma diffusion plate. FIG. 4 is a cross-sectional view of the reactor ofFIG. 2, and FIG. 5 is a magnified cross-sectional view of the firstmixing unit of the reactor of FIG. 4.

Referring to FIGS. 2, 3, 4 and 5, the reactor 100 includes a reactorblock 110 on which a wafer is placed, a shower head plate 120 coupled tothe reactor block 110 using hinges 128 and 129, a diffusion plate 130installed on the shower head plate 120 for spraying a reaction gasand/or inert gas, and a wafer block 140 installed within the reactorblock 110, on which a wafer is seated.

First and second connection lines 121 and 122 are installed on theshower head plate 120, and are connected to first and second connectionpipes 111 and 112 to be described later.

The first and second connection pipes 111 and 112 are installed on thereactor block 110, and connected to the first and second connectionlines 121 and 122, respectively, via a connecting portion 113. An O-ring113 a is installed on the connecting portion 113, and connects the firstand second connection pipes 111 and 112 to the first and secondconnection lines 121 and 122 so that they are sealed when the showerhead plate 120 covers the reaction block 110. When the shower head plate120 is rotated and separated from the reaction block 110, the first andsecond connection pipes 111 and 112 are separated from the first andsecond connection lines 121 and 122.

At least two exhaust holes 117 and 118 for exhausting introduced inertgases and/or reaction gases are formed to be symmetrical to each otheron the bottom of the reactor block 110. A main O-ring 114 is installedon the upper surface of the reactor block 110, so that the reactor block110 and the shower head plate 120 are securely sealed when the showerhead plate 120 is covered.

The shower head plate 120 covers the reactor block 110, so that apredetermined pressure is constantly maintained within the reactor block110. Also, the shower head plate 120 covers the reactor block 110 sothat the diffusion plate 130 is placed within the reactor block 110.

The diffusion plate 130, which sprays a gas during a thin filmdeposition process, has a plurality of spray holes 131, which areconnected to the first connection line 121, and spray a first reactiongas and/or inert gas onto the wafer w, and a plurality of nozzles 133,which are connected to a passage 132 leading to the second connectionline 122 and face the inner side surface of the reactor block 110 tospray a second reaction gas and/or inert gas onto the edges of the waferw.

A first mixing portion 134 for evenly mixing a first reaction gas and aninert gas and flowing the mixture to the spraying hole 131 is formed atthe center of the inside of the diffusion plate 130, as shown in FIGS. 4and 5. The first reaction gas and the inert gas flowing via theconnection line 121 are swirled and mixed, and then diffused and evenlysprayed onto the wafer via all of the spray holes 131.

Spray holes 131 are not formed below the first mixing portion 134 in thediffusion plate 130, as shown in FIGS. 3 and 5. Preferably, the entirearea Al of the diffusion plate 130 having the spray holes 131 is largerthan the area of the wafer w, so that a gas can be evenly spayed overthe entire surface of the wafer.

Preferably, the diameter of the spray holes 131 is between 1 mm and 2.5mm. This diameter, which is obtained by several experiments, allows anexcellent thin film to be formed on the wafer w. Also, the number ofspray holes 131 is about 100 to 1000 according to their diameter. Inthis embodiment, more than 160 spray holes are formed. The cross-sectionof the diffusion plate 130 between spray holes 131 has the shape ofupside-down T, so that thermal energy from the wafer block 140 issmoothly transmitted to the shower head plate 120 in order to preventthe diffusion plate 130 from being overheated.

The nozzles 133 lead to the passages 132 radially formed from a secondmixing portion 135, and are slanted toward the inner side surface of thereactor block 110, as shown in FIG. 4. Preferably, there are 30-100nozzles 133. In the present embodiment, 48 nozzles are formed.

The second mixing portion 135 for evenly mixing a second reaction gasand an inert gas is formed between the second connection line 122 andthe shower head plate 120, as shown in FIG. 4. The second mixing portion135 has a structure in which a hole 135 b is formed through a partition135 a.

The wafer block 140, on which the wafer w is to be seated, is installedwithin the reactor block 110. A heater H is installed in the wafer block140 to heat and maintain the wafer block 140 to a predeterminedtemperature during deposition.

The interval (D) between the diffusion plate 130 and the wafer block 140is in the range of 20 mm to 50 mm. Referring to FIG. 6, which is a graphshowing the interval (D) and specific resistance during deposition of athin film, it can be seen that the specific resistance is the lowestwhen the interval (D) between the diffusion plate 130 and the waferblock 140 is 30 mm. However, when other conditions, for example, thetypes and amounts of first and second reaction gases, the temperature ofa wafer block, or the like, were changed, specific resistance valueswere low at the intervals D within a range of about 20 to 50 mm, and itcan be concluded that the interval D is an important structural propertyin forming an excellent thin film.

The interval within this range is compared to a conventional chemicalvapor deposition (CVD) reactor in which the interval between adiffraction plate to which a reaction gas is sprayed and a wafer blockon which a wafer is seated is about 50 to 100 mm. In the presentinvention, since the interval D is smaller than that in the prior art, adense first reaction gas layer is formed on a wafer w by the pressure ofa first reaction gas and/or inert gas sprayed from the spraying holes131. The first reaction gas layer reacts with a second reaction gasflowed in later, so that a thin film having a higher purity and anexcellent electrical property can be formed.

A pumping baffle 150 is installed around the wafer block 140. Thepumping baffle 150 is made up of a sidewall 150 a installed on thelateral side of the wafer block 140, and a bottom wall 150 b throughwhich symmetrical holes 150 c are formed. A donut-shaped pumping pot 115connected to an exhaust line is formed below the bottom wall 150 b ofthe pumping baffle 150, that is, on the bottom of the reactor block 110.

The sidewall 150 a and the bottom wall 150 b of the pumping baffle 150provide a space in which a second reaction gas and/or inert gas sprayedonto the inner side surface of the reactor block 110 can more evenlyreact to the first reaction gas layer formed on the wafer w. A processproduct generated during deposition of a thin film, and gases not usedduring deposition of a thin film are slipped through the hole 150 c.These gases pass through the exhaust holes 117 and 118, and areexhausted via the pumping pot 115.

When a thin film is deposited, the pressure within a reactor must bemaintained to be 1 to 10 torr. In order to observe and control thispressure, a pressure measuring portion 160 must be installed within thereactor.

The reactor 100 has heaters (H) formed inside and outside to heat thereactor when a thin film is deposited. In this embodiment, when a TiNthin film is deposited, the temperature of the inner surface of thereactor block 110 must be kept at about 120 to 200° C., and thetemperature of the diffusion plate 130 must be kept at about 150 to 260°C. Also, the wafer block 140 must be kept at a temperature of about 425to 650° C., and the pumping baffle 150 must be kept at a temperature ofabout 150 to 230° C. The temperature of a vat valve 101 between thereactor 100 and a transfer module 102 for supplying and transferring awafer w must be maintained at about 140 to 170° C.

In the reactor 100, in a state where the wafer w transferred via thewafer transfer hole 116 is seated on the wafer block 140 and heated to apredetermined temperature, a first reaction gas and/or inert gas issprayed onto the wafer w through the spray holes 131 of the diffusionplate 130 along a route from the first connection pipe 111 to the firstconnection line 121, and a second reaction gas and/or inert gas issprayed onto the edges of the wafer w through the nozzles 133 along aroute from the second connection pipe 112, to the second connection line122, and to the passage 132. The first and second reaction gases areused to form a thin film on the wafer w, and process products or gasesnot used for depositing a thin film are exhausted to the outside throughthe exhaust holes 117 and 118 and the pumping pot 115.

As shown in FIG. 1, the gas jungle includes a first reaction gas supplyportion 210 for supplying a reaction gas to the reactor 100, and asecond reaction gas supply portion 230 for supplying a second gas to thereaction gas 100.

The first reaction gas supply portion 210 is connected to the reactor100 via a first reaction gas supply line 220, and the second reactiongas supply portion 230 is connected to the reactor 100 via a secondreaction gas supply line 240.

A first inert gas supply line 260 through which an inert gas suppliedfrom the inert gas supply source 250 flows is connected to the firstreaction gas supply line 220, and a second inert gas supply line 270through which an inert gas supplied from the inert gas supply source 250flows is connected to the second reaction gas supply line 240.

The first reaction gas supply portion 210 includes a bubbler 211 forgasifying a first reaction material, a first reaction gas mass flowcontroller (MFC) 212 for controlling the flow of a first reaction gassupplied from the bubbler 211, and first and second valves V1 and V2installed on the line between the bubbler 211 and the first reaction gasMFC 212 for allowing or blocking the flow of a first reaction gas.

A third valve V3 for allowing or blocking the flow of the first reactiongas controlled by the first reaction gas MFC 212 is installed on thefirst reaction gas supply line 220.

The second reaction gas supply portion 230 includes a fourth valve V4for allowing or blocking the flow of a second reaction gas, and a secondreaction gas MFC 232 for controlling the flow of a second reaction gaspassed through the fourth valve V4. A fifth valve V5 for allowing orblocking the flow of a second reaction gas controlled by the secondreaction gas MFC 232 is installed on the second reaction gas supply line240.

A sixth valve V6 for allowing or blocking the flow of a supplied inertgas, a first inert gas MFC 262 for controlling the flow of an inert gaspassed through the sixth valve V6, and a seventh valve V7 for allowingor blocking the flow of an inert gas controlled by the first inert gasMFC 262, are installed on the first inert gas supply line 260.

An eighth valve V8 for allowing or blocking the flow of a supplied inertgas, a second inert gas MFC 272 for controlling the flow of an inert gaspassed through the eighth valve V8, and a ninth valve V9 for allowing orblocking the flow of an inert gas controlled by the second inert gas MFC272, are installed on the second inert gas supply line 270.

Here, the gas jungle includes a first bypass line 280 for allowing afirst reaction gas and/or inert gas to flow directly to the exhaust line400 without passing through the reactor 100, and a second bypass line290 for allowing a second reaction gas and/or inert gas to flow directlyto the exhaust line 400 without passing through the reactor 100.

The first bypass line 280 has a tenth valve V10 connected to the linebetween the first reaction gas MFC 212 and the third valve V3 forallowing or blocking the flow of a first reaction gas to the exhaustline 400, and an eleventh valve V11 connected to the line between thefirst inert gas MFC 262 and the seventh valve V7 for allowing orblocking the flow of an inert gas to the exhaust line 400.

The second bypass line 290 has a twelfth valve V12 connected to the linebetween the second reaction gas MFC 232 and the fifth valve V5 forallowing or blocking the flow of a second reaction gas to the exhaustline 400, and a thirteenth valve V13 connected to the line between thesecond inert gas MFC 272 and the ninth valve V9 for allowing or blockingthe flow of an inert gas to the exhaust line 400.

The first and second bypass lines 280 and 290 are adopted to purge thelines within the gas jungle, when a small amount of gas flowed in whilea material of a first or second reaction gas or an inert gas isexchanged must flow directly to the exhaust line 400 without passing bythe reactor 100, when a contaminating source is generated within thelines, or when a new gas jungle is replaced.

As described above, first and second reaction gases, air orcontaminating sources remaining within lines are purged directly to theexhaust line 400 via the first and second bypass lines 280 and 290 by aninert gas, so that the reactor 100 can be prevented from beingcontaminated. Thus, the first and second bypass lines 280 and 290 arenot used in processes for depositing a thin film, but used only inspecific cases.

The gas jungle further includes a separate inert gas supply line 320 forsupplying an inert gas from the inert gas supply source 310 in order topurge gases and/or contaminating sources remaining in the lines. Theinert gas supply line 320 is organically connected to the first andsecond reaction gas supply portions 210 and 230, the first and secondinert gas supply lines 260 and 270, the first and second bypass lines280 and 290, and the exhaust line 400. The inert gas supply line 320 isconnected to gas lines fundamentally required by a process, via afourteenth valve V14 for allowing or blocking the flow of an inert gasto the first reaction gas supply portion 210, a fifteenth valve V15 forallowing or blocking the flow of an inert gas to the second reaction gassupply portion 230, a sixteenth valve V16 for allowing or blocking theflow of an inert gas to the first inert gas supply line 260, aseventeenth valve V17 for allowing or blocking the flow of an inert gasto the second inert gas supply line 270, an eighteenth valve V18 forallowing or blocking the flow of an inert gas to the first bypass line280, and a nineteenth valve V19 for allowing or blocking the flow of aninert gas to the second bypass line 290.

The gas jungle further includes a cleaning gas supply line 340 connectedto at least one of the first and second reaction gas supply lines 220and 240, in order to clean the reactor 100. In this embodiment, thecleaning gas supply line 340 allows a cleaning gas from the cleaning gassupply portion 330 to flow to the reactor 100 via the first reaction gassupply line 220.

The cleaning gas supply line 340 includes a twenty-first valve V21 forallowing or blocking the flow of a supplied cleaning gas, a cleaning gasMFC 342 for controlling the flow of a cleaning gas passed through thetwenty-first valve V21, and a twenty-second valve V22 for allowing orblocking the flow of a cleaning gas controlled by the cleaning gas MFC342.

The reactor 100, the first and second bypass lines 280 and 290 and thecleaning gas supply line 340 are connected to the exhaust line 400. Athrottle valve TV controlled by the internal pressure of the reactor 100measured by the pressure measuring portion 160, for controlling theamount of an exhausted gas, is installed on the exhaust line 400.Twenty-third, twenty-fourth and twenty-fifth valves V23, V24 and V25 forallowing or blocking the flow of an exhausted gas are also installed onthe exhaust line 400. Here, the first bypass line 280 is connected tothe line between the twenty-third and twenty-fourth valves V23 and V24,and the second bypass line 290 is connected to the line between thetwenty-fifth valve V25 and the exhaust pump 410.

In this gas jungle, a cold spot due to undesired condensation occurringwhen a reaction gas flows may be formed. Since a cold spot badly affectsthe process for depositing a thin film, heaters (not shown) forpreventing generation of a cold spot are installed on the lines.Preferably, the heaters are independently installed at as many areas aspossible along lines, and a temperature gradient is formed along eachline. In this embodiment, the temperature gradient is established to bewithin a range of 40 to 200° C. toward the reactor 100.

In the operation of the first embodiment of an ALD thin film depositionapparatus having such a structure, TiCl₄ is used as a first reactiongas, NH₃ is used as a second reaction gas, and Ar is used as an inertgas. Thus, liquid TiCl₄ is contained in the bubbler 211.

The reactor 100 is combined with a transfer module 102 for supplying andtransferring a wafer w, via a vat valve 101, as shown in FIG. 7. Thewafer w is transferred into the reactor 100 via a wafer transfer hole116 using a robot arm (not shown) of the transfer module 102, and seatedon the wafer block 140.

When the wafer w is seated on the wafer block 140, the temperature ofthe wafer block 140 increases within a range of 425 to 650° C., so thatthe temperature of the wafer w is increased to 400 to 600° C. After thewafer temperature is stabilized, the step of introducing a gas into thereactor 100 is performed.

The gas introducing step starts by opening the first valve V1, the sixthvalve V6, the eighth valve V8, and the fourth valve V4 for severalseconds. Then, a bubbled TiCl₄ gas is filled up to the second valve V2,and Ar gas is filled up to the seventh and ninth valves V7 and V9 afterits amount is appropriately controlled by the first and second inert gasMFCs 262 and 272. An NH3 gas is filled up to the fifth valve V5 afterits amount is appropriately controlled by the second reaction gas MFC232.

Next, an inert gas is flowed into the reactor 100 through the seventhand ninth valves V7 and V9. Before a gas is introduced, the internalpressure of the reactor 100 is kept at 10⁻⁴˜5×10⁻³ torr. However, as aninert gas is introduced, the internal pressure of the reactor 100 is 1to 10 torr. This pressure is obtained by the pressure measuring portion160 installed in the reactor 100 appropriately opening the throttlevalve TV of the exhaust line 400. Here, the reason why the seventh andninth valves V7 and V9 are opened after the sixth and eighth valves V6and V8 are opened is that the gas within the reactor 100 may flowbackward through the seventh and ninth valves V7 and V9 when they aresuddenly opened.

The gas introducing step is followed by a step of preventing particlesfrom being generated during deposition of a thin film. Particlesproduced during deposition of a thin film deteriorate the quality of athin film, so the particle generation preventing step is very important.This step is performed by opening the fifth valve V5 at least severalseconds before a TiCl₄ gas is flowed into the reactor 100, while an Argas is continuously flowed into the reactor 100, and introducing an NH₃gas into the reactor 100.

If a TiCl₄ gas is introduced into the reactor 100 before an NH₃ gas isintroduced, part of the TiCl₄ gas reacts to the surface of the diffusionplate 130, which generates particles as byproducts. At this time, theparticle generation preventing step is performed as described above.Particles may be very fine particles of a TiNxCly layer deposited on thediffusion plate 130 or the material Al of the diffusion plate.Accordingly, in order to prevent particles from being generated from thesurface of the diffusion plate 130, an NH₃ gas is introduced severalseconds before an TiCl₄ gas is introduced, so that an NH₃ layer isformed on the surface of the diffusion plate 130. The NH₃ layer on thediffusion plate 130 reacts to a TiCl₄ gas which is introduced duringreal deposition of a thin film, and the TiCl₄ gas is prevented fromgenerating particles from the surface of the diffusion plate 130.

The generation of fine particles is prevented by the principle that aTiCl₄ gas reacts to an NH₃ layer previously formed on the diffusionplate 130 and thus changes to an HCl vapor to be described later, sothat the TiCl₄ gas is prevented from reacting to the surface of thediffusion plate 130 or instantaneously etching the same. The vaporbyproducts are immediately exhausted via the exhaust line 400 to theoutside. A series of reactions occurring within the reactor 110 may beexpressed as in the following chemical formula:2NH3+TiCl4→TiN(s)+4HCl(g)+H2(g)+0.5N2(g).

After the particle generation preventing step, a TiN thin film is reallydeposited on a wafer w by controlling the flow of a TiCl₄ gas and an NH₃gas into the reactor 100.

Deposition of a thin film is performed by alternately introducing aTiCl₄ gas and an NH₃ gas into the reactor 100. It doesn't matter whichgas is introduced first. For example, when a TiCl₄ gas is introducedfirst, a TiCl₄ gas and an Ar gas are first introduced into the reactor,in the first step. After a predetermined period of time, the TiCl₄ gasis excluded. Thus, a TiCl₄ layer is formed on the wafer w, andcompressed by an Ar gas which is continuously introduced.

In the second step, an NH₃ gas and an Ar gas are introduced together.The supply of the NH₃ gas is blocked for a predetermined period of time.The NH₃ gas reacts to the TiCl₄ layer previously formed on the wafer w,thereby forming a TiN thin film on the wafer w. That is, a TiN+NH₃ layeris formed by the consecutive first and second steps.

Next, the first step is again performed to continuously grow a thin filmon the TiN+NH₃ layer. Then, the TiN+NH₃ layer is changed to aTiN+TiN+TiCl₄ layer. Thereafter, the second step is performed to form aTiN+TiN+TiN+NH₃ layer. A TiN thin film having a desired thickness can beobtained by repeating this process.

This TiN thin film deposition process is performed by alternatelyopening and closing the third and fifth valves V3 and V5 in a statewhere the first and fourth valves V1 and V4 are always open, while an Argas is continuously introduced into the reactor 100 by opening thesixth, seventh, eighth and ninth valves V6, V7, V8 and V9.

Here, the second valve V2 is opened before the third valve V3, so that aTiCl₄ gas passes through the first reaction gas MFC 212 and is filled upto the third valve V3. Thereafter, when the third valve V3 is opened tosend a first reaction gas to the reactor 100, the second valve V2 isclosed. That is, a first reaction gas passes through the first reactiongas supply line 220 in units of valves. A process byproduct gasgenerated during reaction is exhausted via the throttle valve TV of theexhaust line 400, and the twenty-third, twenty-fourth and twenty-fifthvalves V23, V24 and V25.

To sum up the above-described reaction, a TiCl₄ gas flows to the firstreaction gas supply line 220 via the third valve V3 after its flow iscontrolled by the first and second valves V1 and V2, and an Ar gas iscontrolled in its flow, passes through the seventh valve V7, is mixedwith the TiCl₄ gas on the first reaction gas supply line 220, and flowsto the reactor 100.

Thereafter, a mixture of TiCl₄ and Ar pass through the first connectionpipe 111 and the first connection line 121, is evenly mixed once more inthe first mixing portion 134, and is evenly sprayed over the wafer wthrough the spray holes 131. An NH₃ reaction gas is controlled in itsflow through the fourth valve V4, and then flows to the second reactiongas supply line 240 via the fifth valve V5. An Ar gas is controlled inits flow, passes through the ninth valve V9, is mixed with an NH₃ gas onthe second reaction gas supply line 240, and then flows to the reactor100. Next, a mixture of NH₃ and Ar pass through the second connectionpipe 112 and the second connection line 122, is evenly mixed once morein the second mixing portion 135, and is sprayed toward the innersidewall of the reactor block 110 through the nozzles 133.

Here, it is preferable that the flow of a TiCl₄ gas is 1SCCM or more,the flow of an Ar gas to be mixed with a TiCl₄ gas is 50SCCM or more,the flow of NH₃ is 50SCCM or more, and the flow of an Ar gas to be mixedwith an NH₃ gas is 60SCCM or more. These values are obtained by severalexperiments. When the flow rates are at least as described above, a thinfilm having a high purity, an excellent electrical property, and a goodstep coverage can be obtained.

In this embodiment, an NH₃ gas is introduced at least one second after aTiCl₄ gas is excluded.

Also, a duration when a TiCl₄ gas and an inert gas are introduced intothe reactor 100, and a duration when the TiCl₄ gas is excluded before anNH₃ gas is flowed into the reactor 100, are at a ratio of 1 to 1.2 orgreater.

The ratio of the flow of an inert gas introduced via the first inert gassupply line 260 to the flow of an inert gas introduced via the secondinert gas supply line 270 is set to be 1 to 1.2 or greater, in order toprevent a strongly-diffusible TiCl₄ gas from flowing backward via thesecond reaction gas supply line 240.

This thin film deposition is achieved by consecutive gas spraying to thereactor 100, and the process pressure of the reactor is maintainedconstant by an appropriate signal exchange and control between apressure measuring portion and valves including a throttle valve.Therefore, the uniformity of a deposited thin film is improved.

While a TiN thin film is deposited on a wafer, Cl can be contained inthe thin film. Since Cl deteriorates the purity and electricalcharacteristics of a thin film, a Cl removing step is also important.The Cl removing step is performed by closing the third valve V3 toprevent introduction of a TiCl₄ gas, and opening the sixth and seventhvalves V6 and V7, the eighth and ninth valves V8 and V9, and the fourthand fifth valves V4 and V5. That is, only an Ar gas and an NH₃ gas aresupplied to the reactor 100. Then, an NH₃ gas reacts to Cl within theTiN thin film formed on the wafer, thereby producing an HCl. The HCl isexhausted to the outside. This Cl removing step can be omitted when thecontent of Cl in a thin film is sufficiently low.

Even when a compound gas containing Ta is used as a first reaction gas,and a compound gas containing N, for example, an NH₃ gas, is used as asecond reaction gas, a TaN thin film can be deposited on a wafer by themethod described above.

A second embodiment of an ALD thin film deposition apparatus accordingto the present invention will now be described with reference to FIG. 8.The same reference numerals as those in FIG. 1 denote the same elements.

In contrast to the first embodiment in which a TiN or TaN thin film canbe deposited on a wafer, a thin film such as a WN thin film can beformed in the second embodiment. In order to achieve the secondembodiment, the first reaction gas supply portion 210 in the firstembodiment is replaced with a first reaction gas supply portion 510. Thefirst reaction gas supply portion 510 includes a thirty-first valve V31of allowing or blocking the flow of a first reaction gas, and a firstreaction gas MFC 512 for controlling the flow of a first reaction gaswhich has passed through the thirty-first valve V31. The first reactiongas supply portion 510 is connected to the third valve V3. WF6 is usedas the material of a first reaction gas, a compound gas containing N,for example, an NH₃ gas, is used as a second reaction gas, and an Ar gasis used as an inert gas.

Deposition of a WN thin film is performed by alternately introducing anNH₃ gas and a WF₆ gas into the reactor 100. For example, when a WF6 gasis first introduced, an Ar gas is introduced together, and the WF6 gasis excluded for a predetermined period of time, in the first step. Then,a WF6 layer is formed on the wafer, and is compressed by an Ar gas whichis continuously introduced. In the second step, an NH₃ gas and an Ar gasare introduced together, and the flow of an NH₃ gas is stopped for apredetermined period of time. The NH₃ gas reacts to the WF6 layer formedon the wafer, thereby forming a WN thin film on the wafer. That is, aWN+NH₃ layer is formed by consecutive first and second steps.

Next, the first step is again performed to continuously grow a thin filmon the WN+NH₃ layer. Then, the WN+NH₃ layer is changed to a WN+WN+WF6layer. Thereafter, the second step is performed to form a WN+WN+WN+NH₃layer. Therefore, a WN thin film having a desired thickness can beobtained by repeating this process.

A third embodiment of an ALD thin film deposition apparatus according tothe present invention will now be described with reference to FIG. 9.The same reference numerals as those in FIG. 1 denote the same elements.

In contrast to the first embodiment in which a TiN or TaN thin film canbe deposited on a wafer, a thin film such as a Ti or TiAlN film as wellas a TiN or TaN film can be formed in the third embodiment. In order toachieve this, the third embodiment further includes a third reaction gassupply portion 620 for supplying a third reaction gas TriMethylAluminum(TMA) to the second reaction gas supply line 240, and a fourth reactiongas supply portion 610 for supplying a fourth reaction gas H2 to thesecond reaction gas supply line 240.

The fourth reaction gas supply portion 610 includes a thirty secondvalve V32 for allowing or blocking the flow of supplied H2, a fourthreaction gas MFC 612 for controlling the flow of H2 which has passedthrough the thirty second valve V32, and a thirty third valve V33 forallowing or blocking the flow of H2 controlled by the fourth reactiongas MFC 612.

The third reaction gas supply portion 620 includes a bubbler 621 forgasifying a third reaction material, a third reaction gas MFC 622 forcontrolling the flow of a third reaction gas, a thirty fourth valve V34installed on the line between the bubbler 621 and the third reaction gasMFC 622 for allowing or blocking the flow of the third reaction gas, anda thirty fifth valve V35 for allowing or blocking the flow of the thirdreaction gas, which has been controlled by the third reaction gas MFC622, to the second reaction gas supply line 240.

That is, in this structure, a compound gas containing a transfer metalelement Ti or Ta is used as a first reaction gas, an Ar gas is used asan inert gas, a TMA gas is used as a third reaction gas, and an H2 gasis used as a fourth reaction gas.

The third embodiment of the thin film deposition apparatus having such aconfiguration is almost the same as the first embodiment, so it will notbe described in detail.

In all of the embodiments described above, a TiCl₄ gas or a compound gascontaining a transfer metal element such as Ti, Ta or W is used as afirst reaction gas. However, other gases can be used as the firstreaction gas. Other gases such as He or N₂ instead of Ar gas can be usedas an inert gas. Also, other compound gases including N, instead of anNH₃ gas, can be used as a second reaction gas.

In the first, second and third embodiments of an ALD thin filmdeposition apparatus according to the present invention, as to first andsecond reaction gases that have a major role in a thin film depositionprocess, a mixture of a first reaction gas an inert gas is sprayed ontoa wafer, and a mixture of an NH₃ gas and an inert gas is sprayed towardthe inner sidewall of a reactor block. The interval between a diffusionplate and a wafer block is narrowed to about 20 to 50 mm, so thatseveral reaction gases react to each other while being sequentiallycompressed down on the wafer. Therefore, a Ti, TiAlN, TiN, TaN or WNfilm having high purity, excellent electrical characteristics, and agood step coverage can be deposited.

Also, an NH3 gas is sprayed to a reactor several seconds before a firstreaction gas is sprayed thereto, so that generation of particles can beprevented.

Furthermore, an NH3 gas is sprayed to a reactor 100 after deposition ofa thin film is completed, or during deposition, so that Cl existingwithin the thin film can be removed. Thus, the electricalcharacteristics of the thin film can be improved.

What is claimed is:
 1. An atomic layer deposition (ALD) thin filmdeposition apparatus comprising: a reactor in which a wafer is mountedand a thin film is deposited on the wafer; a first reaction gas supplyportion for supplying a first reaction gas to the reactor; a secondreaction gas supply portion for supplying a second reaction gas to thereactor; a first reaction gas supply line for connecting the firstreaction gas supply portion to the reactor; a second reaction gas supplyline for connecting the second reaction gas supply portion to thereactor; a first inert gas supply line for supplying an inert gas froman inert gas supply source to the first reaction gas supply line; asecond inert gas supply line for supplying the inert gas from the inertgas supply source to the second reaction gas supply line; and an exhaustline for exhausting the gas from the reactor; wherein the reactorcomprises a first connection line for supplying the first reaction gasand/or the inert gas to the wafer through a plurality of spray holes,and a second connection line for supplying the second reaction gasand/or the inert gas to the wafer through a plurality of nozzles suchthat the first and second reaction gases are alternatively supplied tothe reactor, while the inert gas is continuously supplied to thereactor.
 2. The ALD thin film deposition apparatus of claim 1, whereinthe first reaction gas supply portion comprises: a first bubbler forgasifying a first reaction material to form the first reaction gas; afirst reaction gas mass flow controller for controlling the flow of thefirst reaction gas supplied from the first bubbler; and a first valveinstalled on a line between the first bubbler and the first reaction gasmass flow controller for allowing or blocking the flow of the firstreaction gas.
 3. The ALD thin film deposition apparatus of claim 2,further comprising a second valve installed on the first reaction gassupply line for allowing or blocking the flow of the first reaction gascontrolled by the first reaction gas mass flow controller.
 4. The ALDthin film deposition apparatus of claim 1, wherein the second reactiongas supply portion comprises: a third valve for allowing or blocking theflow of the second reaction gas; and a second reaction gas mass flowcontroller for controlling the flow of the second reaction gas which haspassed through the third valve.
 5. The ALD thin film depositionapparatus of claim 4, further comprising a fourth valve installed on thesecond reaction gas supply line for allowing or blocking the flow of thesecond reaction gas controlled by the second reaction gas mass flowcontroller.
 6. The ALD thin film deposition apparatus of claim 1,wherein the first inert gas supply line comprises a fifth valve forallowing or blocking the flow of a supplied inert gas, a first inert gasmass flow controller for controlling the flow of the inert gas which haspassed through the fifth valve, and a sixth valve for allowing orblocking the flow of the inert gas which has been controlled by thefirst inert gas mass flow controller.
 7. The ALD thin film depositionapparatus of claim 1, wherein the second inert gas supply line comprisesan seventh valve for allowing or blocking the flow of a supplied inertgas, a second inert gas mass flow controller for controlling the flow ofthe inert gas which has passed through the seventh valve, and a eighthvalve for allowing or blocking the flow of the inert gas which has beencontrolled by the second inert gas mass flow controller.
 8. The ALD thinfilm deposition apparatus of claim 1, further comprising: a first bypassline for allowing the first reaction gas and/or inert gas to flowdirectly to the exhaust line without passing through the reactor, thefirst bypass line having a ninth valve for allowing or blocking the flowof the first reaction gas to the exhaust line and an tenth valve forallowing or blocking the flow of the inert gas to the exhaust line; anda second bypass line for allowing the second reaction gas and/or inertgas to flow directly to the exhaust line without passing through thereactor, the second bypass line having a eleventh valve for allowing orblocking the flow of the second reaction gas to the exhaust line and atwelfth valve for allowing or blocking the flow of the inert gas to theexhaust line.
 9. The ALD thin film deposition apparatus of claim 8,further comprising a separate inert gas supply line for purging andexhausting the gas and/or contaminating sources existing within lines,wherein the separate inert gas supply line is organically connected tothe first and second reaction gas supply portions, the first and secondinert gas supply lines, the first and second bypass lines, and theexhaust line.
 10. The ALD thin film deposition apparatus of claim 1,wherein the first reaction gas is a TiCl₄ gas or a compound gascontaining Ta, and the second reaction gas is NH₃.
 11. The ALD thin filmdeposition apparatus of claim 1, wherein the first reaction gas supplyportion comprises: a thirteenth valve for allowing or blocking the flowof the first reaction gas; and a third reaction gas mass flow controllerfor controlling the flow of the first reaction gas which has passedthrough the thirteenth valve.
 12. The ALD thin film deposition apparatusof claim 11, wherein the first reaction gas is WF₆, and the secondreaction gas is NH₃.
 13. The ALD thin film deposition apparatus of claim1, further comprising: a third reaction supply portion for supplying athird reaction gas to the second reaction gas supply line; and a fourthreaction supply portion for supplying a fourth reaction gas to thesecond reaction gas supply line, wherein the fourth reaction gas supplyportion has a fourteenth valve for allowing or blocking the flow of afourth reaction gas, a fourth reaction gas mass flow controller forcontrolling the flow of a fourth gas which has passed through thefourteenth valve, and a fifteenth valve for allowing or blocking theflow of the fourth gas which has been controlled by the fourth reactiongas mass flow controller.
 14. The ALD thin film deposition apparatus ofclaim 13, wherein the third reaction gas supply portion comprises: asecond bubbler for gasifying a third reaction material to form the thirdreaction gas; a fourth reaction gas mass flow controller for controllingthe flow of the third reaction gas supplied from the second bubbler; asixteenth valve installed on a line between the second bubbler and thefourth reaction gas mass flow controller for allowing or blocking theflow of the third reaction gas; and a seventeenth valve for allowing orblocking the flow of the third reaction gas, which has been controlledby the fourth reaction gas mass flow controller, to the second reactiongas supply line.
 15. The ALD thin film deposition apparatus of claim 14,wherein the first reaction gas is a compound gas containing a transfermetal element selected from the group consisting of Ti, Ta and W, andthe second reaction gas is NH₃.
 16. The ALD thin film depositionapparatus of claim 14, wherein the third reaction gas isTriMethylAluminum (TMA), and the fourth reaction gas is H₂.
 17. The ALDthin film deposition apparatus of claim 1, wherein the reactor furthercomprises: a reactor block for receiving the wafer; a shower head platecovering the reactor block to maintain a predetermined pressure withinthe reactor block; and a diffusion plate installed on the shower headplate, and including the plurality of spray holes which face an uppersurface of the wafer to spray the first reaction gas and/or the inertgas onto the wafer, and the plurality of nozzles which extend toward aninner side surface of the reactor block to spray the second reaction gasand/or the inert gas toward edges of the wafer.
 18. The ALD thin filmdeposition apparatus of claim 17, wherein the reactor further comprises:a wafer block installed in the reactor block, on which the wafer is tobe seated; and an exhausting portion connected to the reactor block forexhausting the first and second gases and/or the inert gas from therector block.
 19. The ALD thin film deposition apparatus of claim 17,wherein the reactor further comprises first and second connection pipesconnected to the first and the second connection lines, respectively;and wherein the first reaction gas and/or the inert gas is sprayed tothe wafer through the spray holes along a first route from the firstconnection pipe to the first connection line, and the second reactiongas and/or the inert gas is sprayed to the edges of the wafer throughthe nozzles along a second route from the second connection pipe to thesecond connection line.